Antimicrobial Interventions to Reduce Shiga Toxin-Producing Escherichia coli (STEC) Surrogate Populations on Beef Striploins Intended for Blade Tenderization

ObjectivesBlade tenderization (BT) is used in the beef industry to improve tenderness of steaks prepared from subprimals but can translocate surface pathogens to the interior of meat. Application of antimicrobial solutions on the surface of subprimals prior to blade tenderization can reduce the risk of translocation of surface microorganisms. The objectives of this research were: 1) evaluate the efficacy of antimicrobial interventions applied to inoculated (surrogate Escherichia coli) beef striploins prior to blade tenderization; and 2) examine the transfer of E. coli from inoculated striploins to subsequent non-inoculated subprimals.Materials and MethodsThe anterior portion of whole muscle beef striploins (30.48 cm) were inoculated (lean side) across a 10 cm band with an approximately 8.00 log CFU/mL cocktail containing non-pathogenic, rifampicin-resistant surrogate STEC strains (BAA-1427, BAA-1428, BAA-1429, BAA-1430, and BAA-1431). The inoculated striploins were sprayed with (1) levulinic acid (5.0%) + sodium dodecyl sulfate (0.50%) (LVA+SDS), (2) peroxyacetic acid (2000 ppm; PAA; FCN 1666), (3) acidified sodium chlorite (1200 ppm; ASC), or (4) lactic acid (4.5%; LA) by passing through a spray cabinet and blade tenderized, along with an inoculated, non-sprayed control (CON). To evaluate the potential for cross-contamination of subsequent subprimals, an inoculated striploin (for each treatment) was blade tenderized followed by a non-inoculated beef striploin. For each striploin, surface and subsurface samples (2.54 cm wide) were collected from three different locations including the anterior, middle, and posterior end of each striploin. A total of 30 striploins across three replications were randomly assigned to treatment stratification. Sponge samples were also collected from the blade tenderizer (plate of the blade unit and blades) after each treatment group. Data were analyzed using Proc Mixed (SAS Inst., v.9.4; Cary, NC) as a completely randomized split-plot design. Microbial counts for all samples were log transformed and then analyzed for the main effects of antimicrobial treatment, location (anterior to posterior and surface or interior), and their interaction. Differences were considered significant at α ≤ 0.05.ResultsPAA was more effective in reducing E. coli populations (1.80 log CFU/g; P ≤ 0.05) and had lowest recovery of the microorganism from the striploin subsurface compared to other treatments, followed by LVA+SDS (1.00 log CFU/g). E. coli populations gradually decreased (P ≤ 0.05) on the surface and subsurface as sampling moved anterior to posterior. However, E. coli populations were similar (P > 0.05) on the posterior end of inoculated striploins and the anterior end of the subsequent, non-inoculated striploins, indicating transfer of microorganisms from one striploin to the following striploin. E. coli populations of 3.03 log CFU/cm2 and 2.47 log CFU/cm2 were recovered from the plate of the blade unit and the blades of the blade tenderizer. E. coli populations recovered from the plastic plate (3.46 log CFU/cm2) and blades (2.87 log CFU/cm2) of the blade tenderizer were the similar (P > 0.05) for all treatment groups except for PAA (1.41 log CFU/cm2 and 0.97 log CFU/cm2, respectively).ConclusionThese results showed that PAA and LVA+SDS can be used to improve the safety of blade tenderized beef.

Heat Mitigation Strategies for Finishing Beef Cattle During the Summer in the Southeastern United States Reduces Heat Load and Improves Weight Gain, but does not Influence Meat Quality

ObjectivesThe objective of this research was to determine the effect of heat mitigation strategies on meat quality when finishing cattle under heat stress conditions.Materials and MethodsForty-five Angus crossbred steers (446 ± 23 kg) were blocked by weight and randomly assigned to 1 of 3 finishing environments: shaded with fan (CWF), shaded without fan (CNF), or outside no shade (OUT). For 92 d steers were individually fed a corn-based total mixed ration and were weighed every 3 wk. Environmental monitors (Kestrel Instruments) were used to quantify heat load index (HLI) and accumulated heat load units (AHLU). When the first treatment group averaged 613 kg all steers were harvested. Carcass quality and yield data were collected 24 h postmortem. Strip loins were removed from the right side of each carcass at 24 h postmortem, vacuum packaged, and aged (2 ± 1°C) for 5 d. Strip loins were then fabricated into 2.54-cm steaks anterior to posterior. The first steak was designated for proximate analysis, followed by two steaks for slice shear force (14 and 21 d aging), two steaks for other analyses, and the remaining 7 steaks were randomly assigned to shelf life (SL) for 6 d following 28 d of wet aging. Steaks were vacuum packaged and held (2 ± 1°C) for their respective days of aging. After 28 d, shelf life steaks were opened, placed in Styrofoam trays with PVC overwrap, and placed in retail display cases (1 ± 2°C). Steaks were frozen (–20°C) once they reached their assigned day of wet aging or simulated shelf life. Objective color L* (lightness), a* (redness), b* (yellowness), and isobestic wavelengths were recorded daily (± 2 h). Hue, chroma, DE, and deoxymyoglobin (%Dmb), oxymyoglobin (%Omb), and metmyoglobin (%Mmb) were calculated. Data were analyzed using a mixed model (JMP v.13; SAS) and means were separated using LSmeans at a = 0.05.ResultsEnvironmental monitors showed that CWF and CNF had lower HLI and AHLU (P < 0.01) than OUT. Final weights were greater for CWF than OUT (P = 0.02) while CNF was similar (P ≥ 0.17) to both. Similar results were observed for hot carcass weights where CWF > OUT (P = 0.03), and CNF was similar to both (P ≥ 0.23). Treatment differences were not observed for USDA yield grade (P = 0.38), dressing percent (P = 0.93), kidney pelvic heart fat (P = 0.89), ribeye area (P = 0.47), backfat thickness (P = 0.49), marbling score (P = 0.71), overall maturity (P = 0.92), or subjective lean color (P = 0.16). No differences in fat color scores were observed between CNF and OUT (P = 0.95) while CWF were whiter (P ≤ 0.04) than both. Protein analysis showed CWF had more protein than OUT (P = 0.01) while CNF was similar to both (P ≥ 0.90). No differences were observed for lipid content (P = 0.99), ash (P = 0.39), or moisture (P = 0.92). Treatment nor day of aging effected slice shear force (P = 0.45 and P = 0.53, respectively). While treatment differences were not observed for a*, b*, hue, chroma and DE (P = 0.51, P = 0.65, P = 0.18 P = 0.57, and P = 0.57, respectively). Treatment values for L* were lighter for CNF than CWF (P = 0.04), while OUT was similar to both (P ≥ 0.14). There were no differences for %Dmb, %Omb, and %Mmb (P = 0.24, P = 0.32, and P = 0.39, respectively) among the treatments.ConclusionResults indicate that heat stress mitigation is a viable method to improve weight, however, does not impact the quality of the meat.

STUDIES ON MALARIAL PARASITES : VI. THE CHEMISTRY AND METABOLISM OF NORMAL AND PARASITIZED (P. KNOWLESI) MONKEY BLOOD

1. Normal monkey, Macaca mulatta, plasma and red cells are similar in their inorganic composition to those of human beings. Inorganic phosphate values of plasma and red cells from parasitized monkey blood are lower than normal. Plasma potassium values are higher than normal particularly during segmentation. Other inorganic components of parasitized blood show little variation from normal. 2. Monkey red blood cells parasitized with P. knowlesi consume oxygen in the presence of glucose, lactate, glycerol, and amino acids as substrates. Their respiration is inhibited by cyanide, carbon monoxide, and high oxygen tensions. Normal monkey red blood cells consume oxygen at an appreciable rate only in the presence of methylene blue. 3. Parasitized erythrocytes convert glucose to lactate at a rate 25 to 75 times that of the normal monkey erythrocyte. Unlike the normal red cell, the parasitized cell utilizes lactate if oxygen is present. Lactate is utilized, however, at a rate that is only one-sixth that of its production from glucose. 4. The significance of these findings in relation to the problem of cultivation of malarial parasites is discussed.

STUDIES ON MALARIAL PARASITES : VII. METHODS AND TECHNIQUES FOR CULTIVATION

1. Methods of recovering adequate amounts of Plasmodium knowlesi from the monkey (Macaca, mulatta) for biochemical studies and in vitro cultivation are described. Concentrates of red blood cells parasitized with P. knowlesi can be obtained by differential sedimentation of parasitized blood because of physical and chemical changes produced by the parasites in the host cell and the plasma of the blood. 2. Two different techniques, the rocker-dilution and the rocker-perfusion methods, are described for the cultivation of malarial parasites. Details of the apparatus, assembly, and sterilization are given, as well as methods of counting and evaluating parasites. 3. In a series of 235 control experiments for 20 to 24 hours using three types of apparatus, the average rate of multiplication was 3.9. Each technique has specific value for studying the various aspects of metabolism, nutrition, and the action of antimalarial drugs.

STUDIES ON MALARIAL PARASITES : VIII. FACTORS AFFECTING THE GROWTH OF PLASMODIUM KNOWLESI IN VITRO

1. Methods have been described for the preparation and sterilization of a synthetic nutrient medium which supports normal growth during one 24 hour asexual cycle of the erythrocytic form of P. knowlesi. 2. Successive subcultures with good multiplication can be carried out when whole blood or plasma is added to the medium. Data are presented from two such experiments where the sixth and seventh generations, respectively, were injected into normal monkeys. In both cases, the injections produced clinical malaria and in one, an abnormally severe course was observed. 3. A high percentage (95 per cent) of O(2) inhibits multiplication in in vitro cultures. A gas phase approximating alveolar air permits normal development. A lower percentage (0.37 per cent) of O(2) in the gas phase supports growth at least as well. 4. Certain experiments indicate that in vitro growth is better supported in normal monkey plasma than in plasma from parasitized monkeys. Heating of parasitized plasma to 56 degrees C. for 30 minutes removed the deleterious effect. 5. A nutritional need by the parasite for glucose and p-aminobenzoic acid has been shown. Attempts to demonstrate the need for other individual components of the nutrient medium have not been successful though the effect of the absence of blocks of nutrient such as purines and pyrimidines, amino acids, or water-soluble vitamins can be observed. 6. Further assay of the nutritional requirements of the parasite appears to be hampered by the supply of nutrient furnished by the red cells and plasma. Cultivation of parasitized cells washed free of plasma and resuspended in synthetic medium containing 1 per cent serum albumin has been accomplished as one step directed toward the removal of such interfering factors.

Plasma carotenoid levels in human subjects fed a low carotenoid diet

The purpose of this study was to investigate the effect of a low carotenoid diet on plasma carotenoid levels in humans. Twelve healthy male subjects were fed a low carotenoid diet under controlled conditions for 13 wk in a live-in metabolic unit, as part of a study of vitamin C requirement. Plasma carotenoids (zeaxanthin/lutein, cryptoxanthin, lycopene, alpha-carotene, beta-carotene) were measured with HPLC on study days 2-3, 14-15, 35-36 and 63-64. The rate of decline was rapid between d 2-3 and d 14-15, when the concentration of each carotenoid decreased significantly (P less than 0.05). Although accurate figures for half-life are not possible without more frequent sampling points, mean plasma depletion half-life seemed to be less than 12 d for beta-carotene, alpha-carotene and cryptoxanthin, between 12 and 33 d for lycopene and between 33 and 61 d for zeaxanthin/lutein. Because the decline was not linear over the study period, these data suggest the possibility of at least two body pools of these compounds, with one pool having a more rapid turnover rate. Because there is a significant decline in plasma carotenoid levels within the first 2 wk of a low carotenoid diet, determination of levels of these compounds may be useful only in the assessment of short-term intake.

Glutathione blood levels and other oxidant defense indices in men fed diets low in vitamin C

Because ascorbic acid is an important contributor to the oxidant defense system in body tissues, we studied the effects of a low dietary intake of ascorbic acid on various indicators of oxidant defense and oxidant damage. During a 13-wk study eight healthy men (25-43 y), residing in a live-in metabolic unit, were fed controlled diets containing different amounts of ascorbic acid for four consecutive periods: period 1 = 250 mg/d for 4 d; period 2 = 5 mg/d for 32 d; period 3 = 10 or 20 mg/d for 28 d and period 4 = 60 or 250 mg/d for 28 d. Measurements were made at several time intervals of the activities of glutathione peroxidase and superoxide dismutase in RBC, DNA strand breaks in mononuclear leucocytes, glutathione concentrations in plasma and RBC and NAD and NADP in RBC. After 60 d of low ascorbic acid intakes and associated with plasma ascorbic acid levels less than 6 mumol/L, the total glutathione concentration and the reduced glutathione:oxidized glutathione ratio were decreased in plasma. At the same time NAD and NADP levels in RBC were elevated. It seems that chronic marginal vitamin C deficiency states may be associated with selected biochemical changes in oxidant defense indices.

Biochemical markers for assessment of niacin status in young men: levels of erythrocyte niacin coenzymes and plasma tryptophan

Seven male subjects housed in a controlled metabolic unit for 80 d were fed diets containing amounts of niacin and tryptophan ranging from 6.1 to 32 niacin equivalents (NE) per day. Erythrocyte nicotinamide adenine dinucleotide (NAD) and nicotinamide nucleotide phosphate (NADP), activity of nicotinic acid mononucleotide phosphoribosyltransferase (NMNPRT), plasma tryptophan levels and the urinary excretion of organic acids were measured during dietary periods of low (6.1 or 10.1), adequate (19) and high (25 or 32) NE intake. With both low NE diets, NAD levels in erythrocytes decreased by approximately 70% and increased during repletion with an adequate NE diet. NADP levels remained relatively unchanged. Plasma tryptophan levels decreased by 40% and 10% in subjects ingesting diets of 6.1 and 10.1 NE/d, respectively. A daily 7.8-g leucine supplement during repletion was not associated with changes in plasma tryptophan levels or erythrocyte NAD and NADP levels at the end of the period. No changes in NMNPRT activity or organic acid excretion were found during the study. The results indicate that the erythrocyte NAD level may serve as a sensitive indicator for the assessment of niacin status. Also, a niacin index, the ratio of erythrocyte NAD to NADP, below 1.0 may identify subjects at risk of developing a niacin deficiency.

Hepatic poly(ADP ribose) polymerase activity in methyl donor-deficient rats

Hepatic poly(ADP ribose) polymerase (EC 2.4.2.30) activity as an indicator of DNA damage was measured in rats fed a low methionine, choline-devoid diet (MCD) for a 3-wk period. Additional groups of rats were either injected intraperitoneally (i.p.) with large doses of nicotinamide (NAM) or saline or fed the MCD diet without folic acid (MCFD). As a positive control, some rats were fed the MCD diet supplemented with methionine and choline (MCD + Met). In all groups of methyl donor-deficient rats and associated with increases in hepatic lipid levels, hepatic malondialdehyde concentrations were found to be increased. This observation is evidence for the occurrence of lipid peroxidation in methyl donor deficiency. Methyl donor deficiency was also associated with a significantly elevated hepatic poly(ADP ribose) polymerase activity in all groups of rats as compared to the positive control, suggesting a stimulation of DNA repair processes. The highest enzyme activity was observed in the MCD-NAM i.p. group.

Hepatic content of S-adenosylmethionine, S-adenosylhomocysteine and glutathione in rats receiving treatments modulating methyl donor availability

Because of evidence linking methyl group deficiency and increased tumor formation in experimental animals, we explored other possible methods of producing a methyl group deficiency. Rats fed a low methionine diet lacking choline (MCD) were injected intraperitoneally daily for 3 wk with large doses of nicotinamide. Hepatic levels of lipids were elevated, S-adenosylmethionine (SAM) levels and the SAM:S-adenosylhomocysteine (SAH) ratio were decreased, and SAH level was not consistently changed. In livers of rats fed the MCD diet without folate (MCFD), lipids were also elevated and SAM reduced as compared to MCD-fed rats. In rats fed the MCD diet plus a methionine (Met) supplement (MCD + Met), hepatic SAM levels and the SAM:SAH ratio were higher and lipid levels lower than in MCD-fed rats, indicating that the MCD diet is marginally deficient in methyl donor groups. The injection of nicotinamide or the removal of folate from the MCD diet increased the severity of methyl donor deficiency, as shown by lower hepatic SAM levels and higher hepatic lipid levels. Hepatic glutathione levels were similar in MCD- and MCFD-fed rats and were lower than in rats fed the methionine-supplemented MCD diet or injected with nicotinamide.

Biochemical markers for assessment of niacin status in young men: urinary and blood levels of niacin metabolites

Biochemical markers of niacin status were studied in healthy young men fed 6.1 to 32 niacin equivalents (NE) per day over an 11-wk period while residing in a metabolic unit. Methylated metabolites of niacin, N1-methylnicotinamide (NMN) and N1-methyl-2-pyridone-5-carboxamide (2-pyr), in urine and plasma were determined during periods of low (6.1 or 10.1 NE per day), adequate (19 NE per day = 1 RDA) and high (25 or 32 NE per day) niacin intakes and after small test doses of nicotinamide. Urine excretion of less than 1.2 mg/d of either NMN or 2-pyr was a reliable indicator of subjects receiving the lowest intake of 6.1 NE/d, but the NMN metabolite was a better marker of subjects ingesting 10.1 NE/d. The ratio of 2-pyr/NMN in urine was not as good a measure of the 6.1 NE/d intake as the individual metabolite excretions and was not responsive to the 10.1 NE/d intake. Plasma niacin metabolites were generally not as reliable as urinary metabolites for identifying subjects receiving low niacin intakes, however, values for plasma 2-pyr dropped quickly and were eventually nondetectable. After a 1 RDA oral dose of nicotinamide, increases in urine and plasma 2-pyr levels above pre-dose baseline values were significantly decreased in subjects receiving low, as compared to adequate, niacin intake. A leucine supplement had no effect on the rate of repletion of niacin-deficient subjects nor on the level of methylated niacin metabolites in urine or plasma.

Methylated niacin derivatives in plasma and urine after an oral dose of nicotinamide given to subjects fed a low-methionine diet

Five healthy males, age 25-32 y, were fed in sequence a diet of ordinary foods (10 d, PI), a low-methionine diet (285 mg/d, 14 d, PII), and an adequate-methionine diet (725 mg/d, 7 d, PIII). Diets contained 9 g nitrogen (N) per day with soy protein and synthetic L-amino acids as the N sources in PII and PIII. In PII, subjects were in negative N balance whereas, in PIII, four subjects were in positive N balance. On the last day of each period, fasting subjects ingested a dose of nicotinamide (NAM, 102 mumol/kg body wt). Plasma and urine samples were analyzed for methylated derivatives of NAM by high-performance liquid chromatography (HPLC) methods. Mean values of methylated metabolites in urine from the three diet periods (for four subjects in N balance during PIII) were not different (59.8, 56.7, and 59.9 mumol/(kg body wt X 24 h) for PI, PII, and PIII, respectively). Plasma values of these metabolites also were similar. Results suggest that during a 2-wk period of negative N balance due to a low-methionine intake hepatic methylation processes are not impaired. These processes appear to have a higher metabolic priority than maintenance of the net protein synthesis rate.

Metabolic effects of nicotinamide administration in rats

Male rats fed a 12% casein diet without choline were injected i.p. daily for 2 or 5 weeks with either saline or 6, 20 or 60 mg of nicotinamide (NAM) per 100 g body weight. Weight gain, food intake and gain/food were lower for the NAM-treated groups compared to the controls. Urinary excretion of the major metabolite, N1-methylnicotinamide (NMN) increased with increasing dose of NAM. NAM administration did not alter the activity of hepatic nicotinamide methyltransferase. Excretion of another metabolite, N1-methyl-2-pyridone-5-carboxamide (2-PYR) was low and showed minimal changes in response to NAM administration. NAM administration did not affect urinary creatinine excretion. Livers of the NAM-injected groups were hypertrophied, and the total lipid content was increased. Kidney hypertrophy was also noted. Plasma and liver choline levels were decreased in response to NAM administration. We conclude that chronic NAM administration resulted in a methyl-group deficiency state due to the greatly increased need for methylation of NAM.

Determination of nicotinamide and metabolic products in urine by high-performance liquid chromatography

A high-performance liquid chromatographic procedure has been developed for the quantitation of nicotinamide, nicotinic acid, nicotinuric acid, 1-methylnicotinamide and 1-methyl-2-pyridone-5-carboxamide in rat and human urines. The procedure utilizes a Varian Model 5020 liquid chromatograph with a UV detector, and an Altex 15 cm X 4.6 mm Ultrasphere-ODS column, employing a linear ion-pair mobile phase gradient. Solvent A contains 10 mM concentrations of pentanesulfonic acid (PSA), tetramethylammonium chloride (TMA) and KH2PO4, and solvent B contains PSA, TMA and acetonitrile. Different pH values for solvent A vary the retention times and thus the separation of the five compounds. Temperature of the system is critical. The conditions found most satisfactory were pH 3.30 and 24.5 degrees C.

VITAMIN K

During the decade following Dam's first observations on the hemorrhagic syndrome the combined efforts of several groups of investigators have solved many of the important problems connected with the new vitamin. Sources of vitamin K were discovered, methods of extraction and purification devised, the isolation effected, the structure of K(1) worked out and then verified by synthesis, and a promising start made on the therapeutic applications. In addition, simple water soluble compounds with antihemorrhagic properties have been supplied for clinical work. Preliminary results with these compounds are encouraging.